Feedstock Powder Research Articles

Parametrization and characterization of DED printings using recycled AISI 303 powder particles

This study investigates an upcycling solution to transform AISI 303 stainless steel chips into powder feedstock for Direct Energy Deposition (DED) printing. All the chips were transformed into particles, using a disc milling process, in a size range of 38 to 212 μm with irregular shapes. The work proceeded by parametrizing DED printings on a non-preheated AISI 1045 substrate. Then, a wall-like structure was printed and submitted to microstructure, tomography, microhardness, tensile test and fracture analyses. The printed alloy showed a hardness of 220 ± 14 HV0.1 with a reducing tendency from the heat-affected zone to the topmost region, attributed to the formation of oxides and heat accumulation. The bimetallic specimen tensile test showed failure in the substrate region, verifying a good bonding of the interface. Tomography analysis also validated this result.

Effect of feedstock powder size on the microstructure and thermal conductivity of quasi-eutectic LaYbZr2O7 TBCs

The effect of average feedstock powder size on the evolution of microstructure and thermal conductivity are comprehensively analyzed. It was found that the porosity and thermal conductivity of the LaYbZr2O7 coatings were positively correlated with the average powder size. The conventional notion that higher porosity results in lower thermal conductivity is challenged by the above results. The abnormal porosity and thermal conductivity relationship can be ascribed to the density of horizontal cracks which dominates the thermal conductivity reduction. Reducing the average powder size leads to a greater concentration of horizontal cracks and hence reduced thermal conductivity. Moreover, the LaYbZr2O7 coatings not only show significantly lower initial thermal conductivity of under 0.70 W m−1 K−1, but also exhibit stronger sintering resistance in terms of porosity stability and thermal insulation ability compared to the conventional YSZ coatings. The present work affords a new insight in developing advanced thermal barrier coatings with ultralow thermal conductivity.

Effect of heat treatment on the gas-atomized nickel‑aluminum bronze feedstock powders for cold spray

Due to the high strength of the nickel‑aluminum bronze (NAB), the cold spray deposition efficiency of the NAB powders was less than satisfactory. To improve the deformation behavior of powder, different heat treatment strategies were adopted for gas atomized NAB powders and then the heat-treated powders were deposited on NAB substrates using a high-pressure cold spray system. For various powders and their corresponding deposits, a series of related characterizations were performed. The results indicate that the microstructure of the gas-atomized powder was mainly composed of martensitic β′ and bainite α with high hardness, resulting in low deposition efficiency and poor bonding between particles and particles in the prepared deposits. An effective technique of heat treatment can eliminate the non-equilibrium structure in the gas atomized powder, reduce the hardness of the powder, and significantly improve the deposition efficiency and enhance particle interface bonding.

Reliability comparisons between additively manufactured and conventional SiC–Si ceramic composites

AbstractAn additively manufactured reaction‐bonded silicon carbide ceramic composite is fabricated using a bimodal powder feedstock and the binder‐jetting printing technique. On fabricating, the ceramic is investigated to report its composition, mechanical, and thermal properties at room temperature and high temperatures (up to 750). The ceramic has a density of 2.76 g/cc, and shows a hardness of 21.74 GPa, and a flexure strength of 207.5 MPa at room temperature. The mechanical property of flexure strength is used to estimate its failure probability under applied stress, using a Weibull distribution. The mechanical properties and failure probabilities are compared with those of conventionally fabricated reaction‐bonded silicon carbide ceramics reported in the literature. These ceramics were fabricated using methods such as slip‐casting, compacting, and tape‐casting. The comparison is used to elucidate the advantages and areas of improvement of the present additive manufacturing technique for reaction‐bonded ceramics.

Dispersoid coarsening and slag formation during melt-based additive manufacturing of MA754

We have assessed the structural evolution and dispersoid coarsening behaviors of the oxide dispersion-strengthened superalloy MA754 during two different melt-based additive manufacturing techniques – metal laser powder bed fusion (PBF-LB/M) and directed energy deposition (DED). The mechanically alloyed MA754 powder posed challenges for both processes due to its irregular flaky morphology and large particle size. Successful consolidation with PBF-LB/M required increasing the layer height, decreasing the scanning speed, and increasing the laser power relative to typical Ni superalloy printing parameters. The resulting materials contained residual porosity and large Y-Al-oxide slag inclusions which formed in situ. The more prolonged thermal excursion during DED resulted in even larger, mm-scale slag inclusions, which spanned several build layers. In both PBF-LB/M and DED, these inclusions grew at the expense of nanoscale dispersoids, depleting the material of this strengthening phase. These observations motivate alternative approaches for preparing dispersion-strengthened powder feedstocks besides mechanical alloying and highlight the deleterious effects of Al microalloying on dispersoid stability and structure.

The Reusability of AlSi10Mg Powder in Directed Energy Deposition

The low deposition efficiency in directed energy deposition (DED) has prompted the reuse of powders that do not fuse to the builds to make additive manufacturing more sustainable. It is unknown, however, how the properties of the powder and deposited parts change as powders are continuously reused. In this study, AlSi10Mg was investigated for five deposition cycles in DED. Exposing AlSi10Mg powder to DED conditions changes the morphology, size, and flowability. The mechanical properties of AlSi10Mg DED parts decreased after the feedstock powder was reused one time. Notably, no additional significant changes were observed when the powder was further reused.

From raw elements to 3D samples: An economical route for Co-Cr-Mo alloy fabrication

This study explores an efficient and feasible method for production of non-commercial Co-Cr-Mo powder feedstock for Laser Powder Bed Fusion (LPBF), employing mechanical alloying (MA) with following thermal treatment. Elemental Co, Cr, and Mo powders were subjected to MA to create a powder nanostructured composite. Initially, the mechanically alloyed powder had a mixed-phase state, with ε-phase as the main one (about 95 wt%) and impurities of Cr2O3. However, an additional 1.5-hour of isothermal annealing at 400 °C successfully reduced the Cr2O3 impurities and caused oxygen content to decrease, indicating a reduction in residual oxygen in the powder. This annealing process activated diffusion and induced relaxation of residual stresses, evidenced by decreased lattice microstrains: 0.8% for the Co-phase, 0.2% for both the Cr-phase and Mo-phase. Powder subjected to the thermal treatment was then utilized in LPBF to create bulk Co-Cr-Mo samples. The formed samples showed a typical LPBF microstructure represented by uniaxial cells and dendrites, with the distance between these structures not exceeding 3 µm. The samples showed homogenous elemental distribution, mixed-phase composition, and oxygen concentration not exceeding 5 wt%. In terms of mechanical properties, the LPBF samples exhibited a microhardness value of 4300 ± 200 MPa, ductility of 0.85, and yield strength of 1.4·103 MPa. Our method yields results comparable to those obtained from commercially spherical powder, indicating that our cost-effective approach does not sacrifice product quality. It represents a substantial cost reduction, approximately 4.5 times lower than that of commercial spherical powder, thereby highlighting the economic efficiency of our powder feedstock preparation for LPBF. Our findings underscore the potential of mechanically alloyed and thermally treated powder in LPBF. This worthwhile and efficient method of preparation powder feedstock breaks ground for more comprehensive facilities in 3D printing, cut down on cost of production with maintaining the high-quality output.

Laser powder bed fusion of crack-free 6061Al alloy using nano-sized TiO2 modified powders

Growth of coarse columnar grains during solidification easily leads to hot cracking during laser powder bed fusion (LPBF) of Al alloys. This work offers an alternative route to inhibit the formation of coarse columnar grains during LPBF process. The crack-free 6061Al alloy with a refined microstructure was obtained using nano-sized TiO2 modified feedstock powders. After HIPPing, a nearly defect-free sample was obtained with a fracture elongation of 19.5 ± 0.14%. After artificially peak ageing treatment, the TiO2 modified 6061Al alloy fabricated by LPBF exhibits a tensile strength of 336.1 ± 3.5 MPa and the fracture elongation is still 8.1 ± 0.92%. It is believed that the approaches used in this work are also effective for other LPBF fabrication of low-printability Al alloys.

Triple structuration and enhanced corrosion performance of 316L in laser powder bed fusion

This work focuses on the influence of the feedstock powders on the microstructural properties and corrosion behavior of 316 L stainless steel (SS) produced by laser powder bed fusion (L-PBF) from two different suppliers. Microstructural investigations conducted after additive manufacturing reveal many particularities depending on the powders. These microstructural differences lead to a different corrosion behavior in boiling nitric acid containing oxidizing ions. The presence of the triple structuration (grains, large cells, small internal cells) shows a positive effect on intergranular and cellular corrosion resistance. In both cases, L-PBF 316 L SS provides better resistance to intergranular corrosion than wrought 316L SS.

Surface Controlled Silicon Nanoparticles Production and Their Effects on High Capacity and High Cyclability of All-Solid-State Lithium-Ion Batteries

Si nanoparticle is expected as anode for high density Lithium-ion batteries as as it facilitates high capacity and high cyclability simultaneously owing to its structural robustness to suppress fracture during cycled (de)lithiation reactions. Direct TEM observation has revealed that the particle size of 150 nm is the threshold for facture and the particles smaller than 150 nm are anticipated to contribute to the structural stability during cycles. However, the surface of silicon nanoparticle is oxidized spontaneously and the specific surface area increases significantly with decreasing the particle size. Accordingly, the specific oxygen content of the Si active material becomes inevitably high for smaller nanoparticles. High oxygen content in Si anode decreases the initial efficiency and capacityas a result of irreversible silicate formation. Therefore, smaller nanoparticle with a limited amount of oxidation would be ideal and necessary to attain high capacity and high cyclability. However, there is few report on the approach to suppress oxidation of smaller silicon nanoparticles and discuss the effect of size and oxygen content separately. Also, no general understanding of the effect of the particle size and oxygen for the case of all-solid-state batteries (ASSBs). In this work, we have produced Si nanoparticles with differently controlled size and oxygen content by plasma flash evaporation (PFE) from low-cost powder feedstock, and the effect of characteristic oxide surface structure on the battery performance of ASSBs with Argyrodite electrolyte has been identified.We have successfully produced the nanoparticles as small as 20 nm and reduced the oxygen content x in SiOx representation from the standard amount of 0.24 to 0.049. As a result, the initial discharged capacity can be improved by 110% while attaining similar cyclabilities. When we compare the nanoparticles with different sizes ranging from 20 nm to 165 nm and having small oxygen content x < 0.05, although the initial discharged capacities are almost the same for these particles, only the particle with 165 nm shows rapid capacity decay in 10 cycles, whereas the 20 nm and 84 nm particles tend to maintain the capacity similarly. This confirms that the particles smaller than 100 nm are effective to maintain high capacity also in ASSBs under a low 0.1 C-rate condition. Furthermore, XPS analysis revealed that the surface of the particles with less oxidation is composed of suboxide Si-O bond oxide preferentially and the amount of Si-O4 bond is less than the conventional particles covered by the oxide shell, with which the Si-O bond ratio is described by the conventional random bond model. No apparent dependence of the capacity with the amount of Si-O4 bond. However, the surface oxide shell thickness estimated by the Si-O bond amount and the total oxygen content has shown a clear linear correlation with the charged capacity, irrespective of the particle size. This suggests that the surface oxide thickness affects significantly the amount of the lithiation reaction and is ideally as thin as possible to attain high capacity, especially for the case of ASSBs.

In situ TiC reinforced Ti6Al4V matrix composites manufactured via selective laser melting

PurposeCurrent methods for the preparation of composite powder feedstock for selective laser melting (SLM) rely on costly nanoparticles or yield inconsistent powder morphology. This study aims to develop a cost-effective Ti6Al4V-carbon feedstock, which preserves the parent Ti6Al4V particle’s flowability, and produces in situ TiC-reinforced Ti6Al4V composites with superior traits.Design/methodology/approachTi6Al4V particles were directly mixed with graphite flakes in a planetary ball mill. This composite powder feedstock was used to manufacture in situ TiC-Ti6Al4V composites using various energy densities. Relative porosity, microstructure and hardness of the composites were evaluated for different SLM processing parameters.FindingsHomogeneously carbon-coated Ti6Al4V particles were produced by direct mixing. After SLM processing, in situ grown 100–500 nm size TiC nanoparticles were distributed within the α-martensite Ti6Al4V matrix. The formation of TiC particles refines the Ti6Al4V β grain size. Relative density varied between 96.4% and 99.5% depending on the processing parameters. Hatch distance, exposure time and point distance were all effective on relative porosity change, whereas only exposure time and point distance were effective on hardness change.Originality/valueThis work introduces a novel, cost-effective powder feedstock preparation method for SLM manufacture of Ti6Al4V-TiC composites. The in situ SLM composites achieved in this study have high relative density values, well-dispersed TiC nanoparticles and increased hardness. In addition, the feedstock preparation method can be readily adapted for various matrix and reinforcement materials in future studies.

Wear behavior at high temperature of ZrO2–Y2O3 (YSZ) plasma-sprayed coatings

The wear behavior of two plasma-sprayed zirconia–yttria coatings was studied at high temperatures. Agglomerated and sintered, as well as fused and crushed zirconia–yttria feedstock powders were used to manufacture bimodal and monomodal coatings by atmospheric plasma spraying onto an INCONEL 718 substrate previously coated with a NiCrAlY bond coat. The structure of the coatings was analyzed by SEM on their cross section and surface. The samples were subjected to wear conditions by sliding contact through a ball-on-disk test up to 1000 °C, using an alumina ball 6 mm in diameter as the counterbody, on which a load of 5 N was applied. The samples were rotated during 20000 cycles, reaching a speed of 0.10 m·s−1 at the contact area with the counterbody. The porosity, phase, and mechanical properties were determined before and after wear tests. The results indicate that at 25 °C, both coatings have enough mechanical resistance to withstand the tribological conditions they were exposed to. Therefore, low wear rates were produced by ductile deformation. The tribological conditions became more aggressive as the thermal stresses increased with the test temperature, producing cracking, and detaching particles in the coatings tested at 500 and 750 °C. Consequently, high wear rates related to brittle deformation were obtained. However, the transformation of the amorphous phase to the t′-zirconia phase, produced at 1000 °C, increased the hardness of both coatings and, consequently, their wear resistance; thus, the predominant mechanism of damage was ductile deformation, with wear rates similar to those obtained when the coatings were tested at 25 °C.

The effect of powder feedstock and heat treatment on the thermal and mechanical properties of binder jet printed ZrC

Zirconium carbide (ZrC) disks were fabricated using binder jet printing to study the effect of powder feedstock, print parameters, and heat treatment on flowability and final materials properties. A median volumetric particle size smaller than 10 μm was shown to cause the powder to stop flowing during printing. Disks were printed using ZrC with suitable flowability and then heat-treated at temperatures between 1800 °C and 2200 °C for 1 or 5 h. The density, part shrinkage, thermal diffusivity, and fracture strength all increased with increasing temperature and time. The heat-treated disks were then heated to 2200 °C for 5 h and the properties converged for disks of the same particle size, indicating the hottest temperature and longest time of exposure dictates the final properties. Lastly, it was shown that larger particles produce lower density materials with worse thermal diffusivity, most likely because of poor connectivity between particles after heat treatment.

Mechanical and piezoresistive properties of GNP/UHMWPE composites and their cellular structures manufactured via selective laser sintering

In this study, we describe the development of composites comprising ultra-high molecular weight polyethylene (UHMWPE) reinforced with graphene nanoplatelets (GNP), specifically designed for additive manufacturing (AM) of self-sensing structures through selective laser sintering (SLS). We employed ball-milled GNP/UHMWPE powder feedstocks to fabricate standard test specimens and 2D cellular structures with varying GNP content. A comprehensive assessment of their mechanical and piezoresistive properties was carried out under uniaxial tensile loading. The incorporation of 1.5 wt% GNPs into UHMWPE demonstrated a notable increase in crystallinity by ∼28 % and a significant reduction in porosity by about 98 %. These enhancements contributed to a substantial improvement in both strength (∼21 %) and elastic modulus (∼40 %). Moreover, the introduction of 1.5 wt% GNPs resulted in the formation of electrically percolated composites characterized by prominent piezoresistive behavior. These composites exhibited gauge factors ranging from 9.6 to 18 under uniaxial tensile loading. During cyclic tensile loading, the GNP/UHMWPE composite displayed hysteresis in its piezoresistive response due to viscoelasticity, impeding an immediate return to its original state. Additionally, the gauge factors of the 2D cellular structures generally demonstrated lower values compared to those of the parent composite, scaling proportionally with the effective elastic modulus.

Laser powder bed fusion additively manufactured thin lightweight Ti6Al4V features: an experimental investigation on the influence of powder feedstock, geometry, and process parameters on property/quality

Laser powder bed fusion additively manufactured thin lightweight Ti6Al4V features: an experimental investigation on the influence of powder feedstock, geometry, and process parameters on property/quality

Atomized scrap powder feedstock for sustainable Inconel 718 additive manufacturing via LPBF: a study of static and fatigue properties

Atomized scrap powder feedstock for sustainable Inconel 718 additive manufacturing via LPBF: a study of static and fatigue properties

Elevated temperature tribological performance of non-equiatomic CoCrNiTiWx high entropy alloy coatings developed by mechanical alloying and high-velocity oxy-fuel spray

High entropy alloys (HEA) have applications in multiple fields owing to their exceptional mechanical and physical properties. In the current study, mechanical alloyed CoCrNiTiWx (x; a molar fraction, x = 0.5 and 1.5) HEA feedstock powders were deposited on maraging steel substrate using high-velocity oxy-fuel spray (HVOF). The phase evolution and the microstructure of the milled powders and as-sprayed coatings were analysed by X-ray diffraction (XRD) and scanning electron microscope (SEM). The tribological behaviour of CoCrNiTiW0.5 and CoCrNiTiW1.5 HEA coatings at elevated temperatures was studied extensively using a Pin-on-Disc tribometer. The CoCrNiTiW0.5 and CoCrNiTiW1.5 HEA coatings retained the BCC solid solution phases formed during the milling stage. However, additional oxide and intermetallic phases were formed owing to the in-flight oxidation and high temperatures experienced during the HVOF deposition. The deposited coatings exhibited a lamellar structure and good mechanical bonding with the substrate. The porosities of CoCrNiTiW0.5 and CoCrNiTiW1.5 HEA coatings were found to be 1.69 ± 0.32 % and 1.51 ± 0.37 % respectively.Consequently, the CoCrNiTiW0.5 and CoCrNiTiW1.5 HEA coatings displayed average microhardness values of 863 ± 52 HV0.3 and 1025 ± 39 HV0.3, respectively. Further, the wear rates of coatings exhibited a significant reduction at elevated temperatures, owing to the formation of TiO2, NiCr2O4 oxide tribofilms for CoCrNiTiW0.5, and CoCr2O4, NiWO4, WO3 oxides for CoCrNiTiW1.5. The specific wear rate of CoCrNiTiW0.5 HEA coating dropped by 73.6 % from 22.7 ± 2.6 × 10−6 mm3/N-m to 5.99 ± 1.9 × 10−6 mm3/N-m, while CoCrNiTiW1.5 dropped by 78.8 % from 11.86 ± 3.5 × 10−6 mm3/N-m to 2.51 ± 1.5 × 10−6 mm3/N-m, with a rise in the temperature from RT to 600 °C. Likewise, The frictional coefficients of CoCrNiTiW0.5 HEA dropped from 0.504 ± 0.015 to 0.397 ± 0.005, while CoCrNiTiW1.5 HEA dropped from 0.578 ± 0.025 to 0.471 ± 0.004, with a rise in temperature from RT to 600 °C. At room temperature, the wear mechanisms of the as-sprayed CoCrNiTiWx coatings were dominated by adhesive wear. However, at elevated temperatures, a shift towards oxidative wear was observed.

Plasma-sprayed coatings of 62W bioactive glass: Mechanical properties and in vitro behavior

Bioactive glasses, due to their chemical and biological properties, are promising materials for being used in orthopedic applications. In this study, coatings of the novel 62W glass, with a composition in the system SiO2-CaO-P2O5-MgO, were analyzed. The 62W feedstock powder was prepared from a mixture of reagents by the melt-quenching route and deposited onto titanium alloy substrates by atmospheric plasma spray (APS) technique. The cross-section and the phase of the coatings were analyzed by scanning electron microscopy and X-ray diffraction. Mechanical and in vitro tests were conducted on the obtained coatings to evaluate their bioactive ability. The results of the cross-sections show dense coatings with the absence of the characteristic pores that appear when spraying the usual bioactive glasses. The obtained coatings present a bond strength of 32 ± 3 MPa with the substrate without crystalline phases on the microstructure. The presence of magnesium oxide in the composition favours the glass's processing and increases its crystallization temperature and, thus, the proper stacking of the deposited particles. The bioactive capacity of the 62W coatings was demonstrated at short periods after in vitro evaluation in SBF and TRIS/HCl solutions. The study reveals the potential use of 62W glass coatings for bone implant applications.

Synthesis of High‐Purity Monocalcium Phosphate Monohydrate from Crab Shell Waste

AbstractWaste crab shells (CS) have the potential to mineralize CO2, yielding precipitated calcium carbonate (PCC) powder feedstock for use in the synthesis of monocalcium phosphate monohydrate (MCPM) in an acidic condition by partial neutralization of phosphoric acid at 90 °C and varying times (30–120 min), followed by evaporation of the water at 100 °C. The PCC and MCPM products were analyzed using X‐ray powder diffraction, Fourier transform infrared spectroscopy, and the scanning electron microscopy/energy dispersive X‐ray method. After 120 min of stirring, the pure MCPM revealed uniform particle sizes from 1 to 3 μm. The presented MCPM synthesis using the PCC powder precursor may assist in developing a large‐scale MCPM industry while recycling a considerable quantity of CS waste.

Formulating titanium powder feedstocks for metal injection moulding from a clean binder system

Impurity control is paramount in achieving success in titanium metal injection moulding (Ti-MIM), primarily due to Ti being a universal solvent for interstitial elements such as oxygen and carbon. This study developed a clean binder system with a low decomposition temperature based on polypropylene carbonate/polyoxymethylene (PPC/POM). However, due to the poor shape retention of the PPC/POM binder system, polyethylene glycol (PEG) was incorporated to facilitate the formation of a porous network within the compact structure, allowing efficient removal of residual binder for subsequent debinding process. The results reveal that increasing the PEG content leads to a higher binder removal rate, while adding POM enhances shape retention during debinding. The optimal PEG/PPC/POM binder system compositions were identified as 40/48/10% w/w, respectively, offering a higher PEG removal rate and improved shape retention. Lastly, the resultant debound titanium feedstock from this novel binder system showed low impurity contents, complying with ASTM F2989 requirements.